A large number of structural or system components which must be protected against elevated temperatures in order to guarantee proper operational reliability are found on board an aircraft. Components which emit heat must therefore usually be thermally insulated in order for the structural or system components in the heat-affected zone to remain functional. It is also necessary to protect on-board system components which are relevant to flight safety against the thermal effects of a fire is on board the aircraft through appropriate constructional measures. Furthermore, it may be advisable to thermally insulate heat-emitting on-board system components, in particular in aircraft which are used for military purposes, in order to prevent the emission of a thermal signature which would enable the aircraft to be identified or located.
The transmission of thermal energy from a thermal energy source at an elevated temperature level to the environment takes place through heat conduction, heat radiation and convection. The object of conventional insulating elements is to reduce the heat conduction between the thermal energy source and the environment. Temperature equalisation between the thermal energy source and the environment, which occurs as a result of a heat flow emitted from the thermal energy source to the environment, is thereby prevented or at least delayed in time. Conventional insulating elements therefore usually comprise materials of a low thermal conductivity such as, e.g. air, mineral fibres, foam materials or the like. The low thermal conductivity of the insulating materials reduces the heat conduction between the thermal energy source and the environment, so that sensitive components which are disposed in the environment of the thermal energy source can be protected against the elevated temperature of the thermal energy source.
However, the use of conventional insulating elements in an aircraft has a number of disadvantages. On the one hand, only certain insulating materials are suitable for use on board an aircraft with regard to their insulating properties. For example, the insulating effect of air is frequently not sufficient to fulfill the requirements to be met by an insulating material in a special aircraft application. Moreover, the use of insulating elements comprising an insulating material inevitably results in an increased weight which, for example, must be additionally carried by the aircraft structure, which is designed for high accelerations. On the other hand, the insulating materials which are used in conventional insulating elements may suck up fluids such as, e.g. fuel or de-icing fluid, which must be taken into account in the design and maintenance. Finally, the insulating material of conventional insulating elements may undergo local segregation due to vibrations which occur in particular during flight and as a result lose its insulating capability.
DE 296 14 251 U1 discloses an insulating element with a layered structure which comprises two opposing cover layers and an intermediate layer disposed between the cover layers. The intermediate layer comprises a granulate material, wherein vent openings are provided in the intermediate layer.
DE 7238992 U1 discloses the manufacturing of housings or housing parts for example sidewalls, bottom plates, ceiling plates or covers of sound dampening and insulating layered plates. If needed, the layered plates can be provided with vent openings.
U.S. Pat. No. 3,364,639 relates to an insulating panel comprising an outer housing, an inner housing as well as a fiber core disposed within the inner housing. The inner housing is formed and disposed in the outer housing such that a free space is provided between the inner housing and the outer housing.
U.S. Pat. No. 3,249,659 relates to a panel having a honeycomb structure and two opposing foam plates defining a space therebetween which is interrupted by supporting elements of the honeycomb structure. Outer faces of the foam plates are covered with a layer made of paper, glass fiber material, metal foil or plastics.
DE 10 2004 014 248 A1 discloses a low pressure insulating panel which is made of a self supporting, stable material having a low heat conductivity. The panel is evacuated by means of a vacuum pump and maintained at a predetermined low pressure by means of a controller.
The object of the present invention is to provide a thermal insulating element having a good insulating effect and a low weight which is in particular suitable for use in an aircraft.
This object is solved by a thermal insulating element having the features described below.